A very successful filter for filtering tap water exiting a bottle is shown and described in U.S. Pat. No. 5,609,759 (the disclosure of which is hereby incorporated by reference herein). The carbon block element that is the preferred filtering material there is very effective in reducing the level of chlorine in the tap water, e.g. reducing the level of chlorine in water passing therethrough by at least 50% at a flow rate of 5 ml/sec., and the material also is capable of reducing the levels of some other contaminants. However the filter of the U.S. Pat. No. 5,609,759 patent essentially must be used with tap water, or another relatively pure source of water, because it is incapable of removing biological materials that can be hazardous to human health, such as protozoa, bacteria, and viruses. These biological contaminants have a very small size. For example protozoa are typically in the size range of 3 to 6 microns, and bacteria are normally about 0.6 microns or above in size. The materials used in the carbon block filter of the U.S. Pat. No. 5,609,759 patent cannot, with present technology, be made with a porosity low enough to effectively filter out biological materials. However ceramic materials, using present technology, can be made with a porosity low enough so as to effectively filter out biological materials.
Conventional ceramic anti-microbial filters for use with potentially contaminated water supplies use a pressurized flow of water (e.g. generated by a powered, or hand operated, pump) to develop sufficient pressure to force the water through the sub-micron ceramic filter. Viruses are typically eliminated by the addition of chlorine or iodine directly to the water prior to filtering, or by the addition of a biocidal media such as an iodated resin which functions as a contact biocide. It has not heretofore been practical to provide ceramic filters that are used in essentially unpressurized systems, that is systems with no more than about 24 inches of water head pressure, and therefore ceramic filters have not been suitable for use in sports bottles configurations, such as disclosed in U.S. Pat. No. 5,609,759.
According to the present invention a ceramic filter assembly is provided that is suitable for use in bottles, that is allowing effective filtering even with an initial head pressure of no more than about 24 inches of water. This is accomplished according to the present invention by utilizing a ceramic filtering element that has a pore size percentage which is significantly higher than in conventional pressurized systems. While in conventional pressurized systems the pore size percentage is rarely over about 20%, utilizing the ceramic filtering material in the ceramic filter assembly according to the invention the pore size percentage is between about 40-85%, typically over 50%. The pore size of the ceramic filtering material utilized according to the invention is typically about 0.55 microns or lower, desirably less than 0.5 microns, and optimally about 0.4-0.45 microns. With such a pore size, essentially all bacteria and protozoa cysts are removed by size exclusion alone. If bacteria filtering is not necessary, then the pore size can be opened up so that it is not greater than 3.0 microns.
Also according to the present invention it is highly desirable to provide for effective removal of viruses without requiring the use of chlorine, iodine, iodinated resins, or the like, which can significantly adversely affect the taste of the water. According to the invention the ceramic filter element may include a positively charged coating on the external surface thereof capable of attracting and holding negatively charged viruses, such as the plasma film layers according to U.S. Pat. No. 5,723,219 (the disclosure of which is hereby incorporated by reference herein).
The invention provides a relatively low coat yet effective mechanism for removal of bacteria and protozoa, and optionally viruses, which is convenient, readily usable, totally portable, and inexpensive compared to conventional products.
According to one aspect of the present invention a ceramic filter assembly for use with a bottle having a circular cross-section neck or open end to simultaneously cap the neck or open end, and filter liquid poured out of the bottle through the neck or open end is provided. The assembly comprises the following components: A self-supporting ceramic filtering material element, having a pore size of about 0.55 microns or less (e.g. less than 0.5 microns, for example about 0.4-0.45 microns), through which water may pass at a rate of 2 ml/sec. or more (e.g. about 3 ml/sec. or more, for example about 3-6 ml/sec.) with an initial head pressure of no more than about 24 inches of water, the element having first and second ends. A cap element operatively connected to the ceramic filtering material element first end, and having a liquid passage therein, so that water flows through the ceramic filtering element and is filtered, and then flows through the liquid passage. And, the cap element having surface manifestations that are cooperable with a bottle neck or open end to releasably connect the cap element to a bottle neck or open end, so that water may be dispensed from a bottle by passing from within a bottle through the ceramic filtering material element, and then through the cap element liquid passage, and out the bottle.
The ceramic filtering element material is preferably substantially tubular having an interior void volume with a first at least partially open end, and a second closed end, the first end operatively connected to the liquid passage. A manual valve, such as a conventional bicycle bottle reciprocating valve (i.e. a push-pull valve), may be connected to the cap element for selectively allowing or preventing passage of water through the liquid passage.
The ceramic filtering material preferably has an open volume of between 40-85%, typically over 50%, e.g. about 51-80%. It may be self-venting in use (that is not requiring a separate vent in the cap element), or a distinct vent may be provided in the cap element. The ceramic filtering material preferably comprises a binder and clay composition, which is proprietary product developed by and available from Water Protection, Inc. of Miami, Fla.
The filter assembly may further comprise a second filter element (or even more filter elements) comprising a substantially continuous body of activated carbon and binder capable of reducing by at least 50% (and typically over 80 or even over 90%) the chlorine in water passing therethrough. The second filter element may be disposed within the void volume of the ceramic filtering material element. Other filtering material that may be used in place of or in addition to the carbon block filter include a monolithic composite (which may include carbon) incorporating polymer extraction technology for the removal of lead, arsenic, and nuclear contamination, etc.
The cap element preferably has a first seal defining surface, and the ceramic filtering element has a second seal defining surface; and the second filter element has a third seal defining surface; and the invention further comprises at least first and second seal elements cooperating between the first and third seal surfaces, and the second and third seal surfaces, respectively, to allow replacement of the second filter element with respect to both the cap and the ceramic filtering element, while substantially preventing flow of liquid between the seal surfaces.
The ceramic filter element comprises an external surface, and the assembly according to the invention also preferably further comprises a positively charged coating on the external surface capable of attracting and holding negatively charged viruses. For example the positively charged coating comprises a plasma film comprising a first layer containing a first functional group and a second layer containing a second functional group (e.g. amines) which is deposited on at least one of the periphery and the interstitial spaces of the ceramic filter (such as shown in U.S. Pat. No. 5,723,219).
The assembly may also comprise a straw receptacle provided in the cap element and at least in part defining the liquid passage. Other details of the assembly, such as the particular mounting structure and the like, may be as provided in U.S. Pat. No. 5,609,759 or in co-pending application Ser. No. 09/008,845 filed Jan. 20, 1998 (the disclosure of which is also incorporated by reference herein).
According to another aspect of the present invention a method of filtering water containing dangerous biological material including bacteria and protozoa using a ceramic filter element mounted in a bottle having an open end, is provided. The method comprises: (a) Placing water containing dangerous biological material including bacteria and protozoa into the bottle. And, (b) using only human generated pressure, causing the water to flow through the ceramic filter element out of the bottle open end at a rate of at least about 2 ml/sec, the ceramic filter element removing substantially all bacteria and protozoa from the water. In the practice of the method, (b) is typically practiced by inverting the bottle so that the open end thereof is near the bottom, squeezing the bottle, or both inverting and squeezing the bottle, dispensing of the water in this manner being possible because of the relatively large open volume (e.g. between about 40-85%) of the ceramic filter so that a non-pressurized system (e.g. one requiring no more than about 24 inches of water initial head pressure) is provided. Alternatively (b) may be practiced by placing a straw into the bottle separated from the water containing dangerous biological material by the ceramic filter, and sucking through the straw. Typically the ceramic filter has a positively charged porous coating as described above, in which case (b) is also practiced to cause the water to flow through the coating so that negatively charged viruses in the water are removed by the coating.
The method may also be practiced utilizing a tubular filter as the ceramic filter, the tubular filter having a void volume therein, and also using a second non-ceramic filter element for removing other materials from the water aside from dangerous biological material. In that case the method further comprises (c) removing the existing ceramic filter element and second filter from the bottle; (d) removing the existing second filter from the ceramic filter element; (e) replacing the second filter with a new second filter; (f) placing the new second filter into the existing ceramic filter; and (g) reinstalling the existing ceramic filter element, with new second filter, into the bottle. (c) through (g) may be repeated between 4-about 10 times before the existing ceramic filter is replaced with a new ceramic filter. For example where the second filter is a carbon block filter for reducing the level of chlorine in the water by at least about 50%, the carbon block filter may be replaced about every 30-60 gallons, while the ceramic filter is replaced about every 250 gallons.
According to another aspect of the present invention a bottle with filter assembly is provided comprising: A plastic bottle having an open end. A cap closing the open end and having a closable liquid passage therein. A filter assembly operatively and removably connected to the cap and disposed within the bottle so that water from the bottle must flow through the filter assembly before passing out the cap. The filter assembly comprising a first tubular outer filter element of a first filtering capability and longevity, and a second inner filter element of a second filtering capability and a second longevity, the second longevity less than the first longevity. And, the first and second filter elements being readily detachable from the cap so that the second filter element can be replaced with a new second filter element, and then the first filter element with new second filter element reinstalled into operative contact with the cap and returned to the bottle. In the assembly described above, the cap preferably has a first seal defining surface, and the first filter element has a second seal defining surface, and the second filter element has a third seal defining surface. The assembly also further comprises at least first and second seal elements cooperating between the first and third seal surfaces, and the second and third seal surfaces, respectively, to allow replacement of the second filter element with respect to both the cap and the first filter element, while substantially preventing flow of liquid between the seal surfaces. The first and second seal elements typically comprise O-rings.
According to yet another aspect of the present invention a ceramic filter assembly for use in a bottle having an opening, and insertable through the opening, is provided. The assembly comprises: A self-supporting ceramic filtering material having a pore size capable of filtering substantially all protozoa and bacteria out of water and an open volume of greater than about 50%. And, a mounting structure which mounts the filter material in a bottle so that water passes through the filter material as the water exits the bottle. The assembly further comprises a hydrophilicity enhancing coating on at least one portion of the ceramic filtering material (e.g. the external surface thereof), the coating preferably comprising a plasma film such as described in U.S. Pat. No. 5,723,219. Typically the ceramic filtering material comprises a binder and clay composition having a pore size of about 0.5 microns or less, and an open volume of between about 51-80% (and each particular value therebetween).
It is the primary object of the present invention to provide an effective, readily usable, convenient, totally portable, and relatively inexpensive filter assembly for dealing with biological materials. This and other objects of the invention will become clear from an inspection of the detailed description of the invention and from the appended claims.